FORM AND STRUCTURE 
Sorosis, is a multiple fruit of which the mulberry is an ex- 
ample. 
Strobile or Cone, is a multiple fruit consisting of a scale-bear- 
ing axis, each scale enclosing one or more seeds. Pine 
cones are examples, 
Galbulus, is a cone, the scales of which have become succu- 
lent. The juniper berry is an example. 
The Seed is the fertilized and ripened ovule. It contains the 
embryo and usually more or less albumen. A well de- 
veloped embryo possesses four parts: a tiny stem or 
Caulicle, at the lower end of which is the beginning of a 
root, called a Radicle; and Cotyledons, which are two 
thickened bodies near the upper end of the caulicle, and 
between these is a small bud called a Plumule. These 
parts can be readily seen in the sprouting bean or pea. 
Some plants produce seeds bearing one cotyledon only ; 
such are called Monocotyledones. Others bear two co- 
tyledons, they are called Dicotyledones. 
THE TREE STEM OR TRUNK. 
Stems are of two kinds, Endogenous and Exogenous, so 
named from the character of their growth. In an endogenous 
stem the wood is made up of separate threads scattered, here 
and there, throughout the whole diameter of the stem. In 
an exogenous stem the wood is collected to form a layer sur- 
rounding a central column of pith and is itself surrounded by 
bark. 
A transverse section of a small twig of a tree shows the 
pith in the centre, around it a zone of wood, then a green 
inner bark, and finally the outer bark. All parts, except 
possibly the outer bark, are alive. 
A transverse section of a mature tree exhibits a centre of 
heartwood or Duramen and a zone of sapwood or Alburnum, 
an inner bark and an outer bark. In addition are seen a 
series of concentric rings known as rings of annual growth, 
also a number of lines radiating from centre to circumference 
called Medullary Rays. The pith has disappeared but the 
medullary rays are composed of pith tissue and form a set 
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